The invention relates to a method of recording digital information signals on a removable rewritable disc like recording medium, as cited in the preamble of claim 1. The invention further relates to an apparatus for recording/reproducing digital information signals on/from a removable rewritable disc like recording medium as cited in the preamble of claim 6.
The PC world needs a replacement for the floppy drive. A rewritable storage medium of the disc like optical type, such as the CD-RW, seems to be a logical choice because the read function of the magnetic floppy is already replaced by the CD-ROM. All PC""s today are equipped with a CD-ROM and applications and software are distributed on CDROM. Therefore a recording medium like CD-RW or rewritable DVD, seems to be the perfect media to fill in the needed write capability. MO and ZIP/Jazz already tried to fill this gap, but they all miss compatibility with the installed base. That is exactly what CD-RW for instance can deliver with the installed base of over approximately 200 million CDROM drives (MR1.0 compatible). RW media are cheap and the capacity is sufficient for floppy use.
Furthermore, manufacturers of operating systems wants to get rid of legacy material like the floppy drive. For OEM companies the idea is attractive, as they can replace the floppy drive, the CDROM and the DVD-ROM drive by a one spindle drive like a Combi and by a double writer in the future. It will also add a new feature to the drive other then the ever increasing speed
There are products on the market (like DirectCD) which enable to use a CD-RW like a floppy drive, but they don""t behave the way one would expect a CD floppy drive would do. The access time is too low, formatting time is too long and more important the drive does not fit into the strategy of current OS. The disc should be immediately available for dragging and dropping of files. A fast eject is required, deleting should be instant. Due to enable multiple drag and drop a defect management is required. However, the defect management should be done by the drive. This opens the way to use UDF 1.02 instead of UDF1.5, which will not be supported on the write side by Microsoft. Further background formatting must be done by the drive and not by the application or OS to minimize bus traffic, and interaction between the drive and the OS. Finally, Read/Modify/Write for packets should be done by the drive.
European Patent Application (NL000035), filed by applicant under filing number EP 99203111.2 and European Patent Application (PHN17659), filed by applicant under filing number 00200290.5, both incorporated by reference, are disclosing such a method and apparatus.
However, the method of defect management disclosed is limited to one-packet based replacements, the size of the replacement packets being same to the size of the write-packet. For instance, in case of CD-RW both sizes are 64 kB or 32 sectors. Although this is sufficient to cover Disk-Over-Write (DOW) problems of RW media, it appears to be inefficient with respect to robustness for local physical defects like finger prints, scratches and media weak-spots. DOW tends to wear out sectors equally within one written packets. Thus it makes a lot of sense to replace the whole unity in one step, since the indication that a part (2 kB-sector) of the packet is wearing out can be interpreted as a wear-out warning for the whole packet. But due to the spiral-groove structure of an optical record carrier, non DOW defects, like the ones mentioned above, will typically appear on neighborhood tracks. For example a scratch of 3.5 cm from inner to outer diameter across the disk affects approximately 3.5 cm/1.5 xcexcm=23300 tracks, in case of an CD-RW disk. This implies approximately 21000*64 kByte=1344 Mbyte. With a 74 min CD-RW disc with 500 Mbyte user area and approximately 40 Mb spare area, this is clearly not feasible.
In consequence, amongst other things, it is an object of the invention to obviate above-mentioned disadvantages. According to one of its aspects a method according to the invention is characterized as recited in the characterizing part of claim 1 and an apparatus according to the invention is characterized as recited according to the characterizing part of claim 6.
Local physical defects, not effecting a whole packet, will then require less spare area then if a whole packet would be replaced.
Further advantageous embodiments are characterized as recited in the remaining claims.